Conventionally, a natural single-crystal diamond has been frequently used for a perforated tool, an abrasion-resistant tool, a cutting tool, and the like. Sometimes, a single-crystal diamond synthesized under a high pressure has been used. For example, each of Japanese Patent Laying-Open No. 2000-288804 (Patent Document 1), Japanese National Patent Publication No. 2000-515818 (Patent Document 2), and Japanese Patent Laying-Open No. 2002-102917 (Patent Document 3) discloses a tool insert and a wire drawing die, which include: an insert body and a die main body; and a grindstone chip composed of a natural or artificial diamond.
A single-crystal diamond is absolutely harder than other materials. Hence, even if any type of diamond is employed for perforated tools, abrasion-resistant tools, and cutting tools, these tools are hardly worn and can be used equally. Actually, they are being used with no particular problem.